Single ply roofing systems and methods of constructing them

ABSTRACT

A single ply flexible membrane roofing system secured to a roof deck has a first membrane secured to the roof deck by fasteners. The membrane system includes a second membrane with an edge portion overlapping the first membrane edge which can be “factory” weld-bonded to the first membrane along the edge of the second membrane to provide waterproofing such that the first membrane edge projects forwardly from the bond to define a fastening projection extending forwardly from the weld bond for the laterally spaced fasteners. An adhesive coating over the fastening projection and fasteners extends essentially from the weld bond forwardly to provide a continuous adhesive coating over the first membrane projection and the fasteners to provide a substantially monolithic water-sealed seaming bond of enhanced strength with enhanced resistance to uplift forces. The invention is concerned also with the labor reduced method of constructing the system.

TECHNICAL FIELD OF THE INVENTION

The invention relates to roofing systems of the type secured to generally flat roof decks and comprised of flexible synthetic membranes with overlapped and bonded edges.

BACKGROUND OF THE INVENTION

Single-ply membrane sheet roofing systems are very well recognized and widely in use as both new and renovated exterior roof surfaces for a multiplicity of building structures having generally flat roof decks. Such deck sheets today are custom prefabricated in the factory by Duro-Last, Inc., applicant's assignee, to the exact dimensions of the building roof and furnished, with weight considerations in mind, in rolled transportable sections of up to 2500 square feet to the roofer on site. Other single-ply roofs are largely worker-constructed at the site and bonded by the roofer on the site. Presently, in the case of Duro-Last, Inc. up to eighty-five percent of the field seams can be completed in the factory under ideal factory conditions, eliminating waste, saving labor, and preventing leaks. A number of such roofing systems are utilized for large footprint roofs, such as factories, administrative buildings, schools, and office buildings, for example. The present invention is concerned with improvements which are particularly suited to the more difficult-to-install systems where the number of necessary fasteners utilized, from the standpoint of labor cost, must be kept to a minimum, while still effectively performing their function.

SUMMARY OF THE INVENTION

The present invention is directed to a combination of a first membrane with a longitudinally extending free edge secured to a roof deck by fasteners and a second membrane with an edge portion overlapping the first membrane edge and factory weld-bonded to the first membrane by means of a continuous bond between the substantially very edge of the second membrane so that the first membrane edge projects forwardly from the bond to define a fastening projection or tab extending forwardly upon the roof deck.

When the second membrane is peeled upwardly, back from the bond and fastening projection, the fasteners are placed along the fastening projection to secure the fastening projection of the first membrane to the deck. With the second membrane still in peeled-back position, a fast-drying adhesive is applied over the fastening edge and fastener, from the factory bond forwardly, and provides a continuous adhesive coating from the first membrane projection over the fasteners and fastening tab or projection. Thus, a continuous monolithic bond, including the factory bond, and extending forwardly over and beyond the fastening tab and fasteners is provided in the preferred system illustrated. When the second membrane (which also preferably has its underside appropriately coated with the same adhesive) is lowered to cover the fastening projection and the deck forwardly thereof, a substantially continuous layer of material, created by the factory welding and on site adhesive coating, provides in conjunction with the mechanical fasteners a novel monolithic joint or seam.

One of the prime objects of the invention is to provide a roofing system which is exceptionally resistant to wind up-lift forces in areas of the country in which wind forces are particularly strong and hazardous to roofs.

Another object of the injection is to provide a membrane system in which the fasteners used need not be of the barbed character presently in wide use for gripping the membrane to resist wind up-lift forces.

Another object of the invention is to provide a labor-saving installation requiring a reduced number of fasteners when the roof deck is a difficult structure to roof (such as concrete) which must be drilled to receive the fasteners and is labor and cost intensive.

Another object of the invention is to provide an inexpensive, mechanically secured single-ply roofing system which is extremely durable under a wide range of wind conditions and in a variety of climates.

Another object of the invention is to provide an economically installed single-ply roofing system of reliable sealed quality which is manufactured in substantial part in the factory to ensure quality control in a sheltered working environment with specially trained employees.

Another object of the invention is to provide equal-lateral pull resistance over the fastener lap, thus uniformly spreading up-lift load through the fasteners into the deck.

Other objects and advantages of the invention will be apparent to those skilled in the art. The preferred embodiments disclosed herein are disclosed by way of example and not intended in any way to restrict the language of the claims which follow.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects, features and advantages of the invention will become more readily apparent in view of the following detailed description, appended claims and accompanying drawings, in which:

FIG. 1 is a schematic fragmentary top plan view showing part of a multiple first and second membrane sheet secured to an underlying deck structure;

FIG. 2 is a similar view of the factory supplied roofing sheet only;

FIG. 3 is an enlarged sectional elevational view taken on the line 3-3 of FIG. 1 to illustrate a membrane system in secured position on a roof deck; and

FIG. 4 is an enlarged schematic prospective elevational view illustrating a preferred method of applying the system to a roof deck.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now more particularly to the accompanying drawings, it should be understood that the roofing system, generally designated S, and secured on roof deck D is comprised of a series of membranes, generally designated M, which are factory welded along their lapped edges to form the multiple membrane sheet, generally designated S. In FIGS. 1-4, an adjoining pair of such membranes are numbered generally 10 and 11.

As shown in FIGS. 2-4, the factory weld 12 extends in a longitudinal direction from the outside edge 12 a about an inch to the edge 12 b. This weld can be accomplished in the factory under quality control conditions and may comprise a hot air weld effected by hot air (i.e. at a temperature of around 1200° F.) which heats the sheets 10 and 11 at the edge of sheet 11 to a welding temperature wherein their confronting thermoplastic surfaces partially melt and form a weld bond of material 12. The weld may also be created by a die electric or radio frequency welding process, or other known heat welding or bonding methods. “Factory” welds are recognized to be more reliable than hot air field welds to achieve water-tight seams.

The sheet S, comprised of multiple membranes M, welded in the manner disclosed in the factory, can be supplied to the roofer in rolled sheets of, for example, 2500 square feet in the weld bonded condition shown in FIG. 2. Securement of sheet S to the roof can then take place progressively in the manner indicated in FIG. 4. With the upper sheet 11 peeled back about its welded edge 12 b, fasteners or screws 13 with heads 13 a extending through square countersunk steel load distribution plates 14 anchor the sheet S.

The roof deck D can be comprised of many known surfaces or substrates, such as concrete, wood, asphalt, coal tar, steel, cementitious wood fiber and the like, and, for purposes of illustration only, is shown in FIG. 3 as comprised of an insulation board sheet 15 on a wood deck 16, which may be supported by suitable purlins or deck supporting structures in the conventional manner.

Once the fasteners 13 are secured in position with a suitable rotary power tool, a roller applicator or roller brush, generally designated B, having a handle 16 may be used to apply a fast-drying liquid adhesive to the surface of the fastening tab or projection 10 a, defined by the parting line 12 b forwardly and across the fastening projection 10 a to provide a coating 17 (FIG. 3) completely covering both the fastening projection 10 along with the fastener heads 13 and the plates 14. The completely sealing coating 17 also is applied to the free edge 10 c of the fastening projection 10 a and to the deck member 15 forwardly of the edge 10 c for a predetermined distance 17 a, i.e. six inches (6″). It is preferably applied as well to the underside of the membrane 11 from weld edge 12 b forwardly for a distance so as to mate with the portion 17 a of the coating 17 which is provided on the deck member 15. Because the membranes 10 and 11 are sufficiently flexible, the membrane 11 folds downwardly as at 11 a to follow the edge 10 c and adhesive fills the space between them as at 17 b. Finally, as FIG. 3 indicates the adhesive film 17-17 a feathers out, as at 17 c, on the deck member 15.

As indicated previously, not only is the strip S securely fastened in position mechanically by the fasteners 13 extending through each fastening projection 10, a substantially continuous monolithic bond is formed by the “factory” weld bond 12 and the “field” adhesive coating 17 to interact with the fasteners 13 and prevent wind lift-up forces from applying unevenly and cocking the securing fasteners 13 in a manner to tear the membrane. While various of suitable fast-drying liquid adhesives are possible, one such adhesive which will work to secure the membranes in the field is manufactured by Sovereign Specialty Chemicals of Cincinnati, Ohio. With the present system the number of fasteners 13 which need be used to secure the strip S in terms of resisting wind up-lift is considerably fewer. Resistance to membrane tearing, and membrane peeling particularly, is greatly increased and any tendency to pull the fasteners up at cocked angles rather than straight up is considerably reduced by this monolithic structure.

METHODS OF OPERATION AND CONSTRUCTION

FIGS. 1-4 particularly disclose the method of construction of the roof system and the resulting product. Each overall sheet S is comprised of a number of adjacent membranes 10 and 11, each of which has a fastening projection 10 a formed by overlapping an edge portion of each membrane at the joint or seam. The sheet S is applied in the manner illustrated in FIG. 4, with each of the fastening projections 10 a successively secured in position by fasteners 13 and sealed by adhesive bonding as at 17, 17 b, and 17 a until the end edge of the opposite end of the sheet S shown in FIG. 4 is laid down and secured. The sheet is supplied to the site in a roll which, after the first edge is fully unwound and pealed back to expose each fastener tab 10 a. Tautening “Grip-pull” devices of a conventional nature are used in the usual manner to remove wrinkles as the tabs 10 a are progressively fastened and to keep each membrane taut as it is brought down to the deck to unite the adhesive on the underside of membrane 11 with the adhesive on tab or ledge 10 a and over fasteners 13 and plates 15. If an edge of a sheet S is to be joined to the edge of a membrane, such as a parapet membrane, for example, it may be so joined in any acceptable manner on the site by the roofer, such as by hot-air welding of the overlapped edges with mobile implements, which are well known in the art.

Typically the membranes used may be forty mil membranes, with the membrane consisting of polyester fabric cores coated on each side with polyvinyl chloride or another thermoplastic. Duro-Last, Inc. of Saginaw, Mich., produces highly suitable membranes of this character. Various other roofing membrane sheets, including synthetic rubbers or elastomers such as EPDM and CPE, or others which may be classified as thermoplastic synthetic resins or polymers and are flexible, are believed also suited. While a membrane thickness of 0.040 inches is normal, the membrane size may, for example, be anywhere in the neighborhood of 0.030 to 0.080 in thickness, and may contain various reinforcing materials in the form of fibers or fabrics.

It should be understood that the foregoing disclosure of the invention is descriptive only of preferred forms thereof, and that the spirit and scope of the invention are to be limited only by the terms of the claims appended hereto. 

1. In combination, a single ply membrane roofing system secured to a roof deck; said system comprising a first flexible membrane with a longitudinally extending edge secured to said roof deck by transversely spaced fasteners, said membrane system having a second flexible membrane with an edge portion overlapping said first membrane edge and weld bonded to said first membrane via a continuous weld bond along the edge of said second membrane such that said first membrane edge projects forwardly from said bond to define a fastening projection for said fasteners extending forwardly from said weld bond, and having the improvement comprising: a. an adhesive coating over said fastening projection and fasteners, extending essentially from said weld bond forwardly to provide a continuous adhesive coating over said first membrane projection and fasteners providing a substantially monolithic bond comprising said weld bond and adhesive coating.
 2. The combination of claim 1 wherein said adhesive coating extends down the front edge of said first membrane to provide a coating stepping portion extending down past the front edge of said first membrane to the level of said deck between said first membrane and the underside of said second membrane.
 3. The combination of claim 1 wherein said adhesive coating extends forwardly of said front edge of said first membrane for a short distance between said second membrane and deck.
 4. A method of securing a single ply membrane roofing system to a roof deck; said system comprising a first membrane with a longitudinally extending free edge to be secured to said roof deck by transversely spaced fasteners, said membrane system having a second membrane with an edge portion overlapping said first membrane edge and bonded to said first membrane via a continuous weld bond along the edge of said second membrane such that said first membrane edge projects forwardly from said weld bond to define a fastening projection extending forwardly from said free edge under said second membrane, comprising: a. with said system applied to said roof deck and maintaining said second membrane peeled upwardly back from said weld bond and fastening projection, placing spaced apart fasteners into said deck to secure said fastening projection of said first membrane to said deck; b. with said second membrane in said peeled back position applying a liquid adhesive over said fastening edge and fasteners from said weld bond forwardly to provide a continuous adhesive coating on said first membrane projection and over said fasteners; and c. lowering said second membrane to cover and adhere to said fastening projection and fasteners and provide a substantially continuous monolithic bond comprised of said weld bond and adhesive coating.
 5. The method of claim 4 wherein said adhesive coating flexibly extends down the front edge of said first membrane to the level of said deck between the said front edge of said first membrane and the underside of said second membrane.
 6. The method of claim 5 wherein said adhesive coating extends forwardly of said front edge of said first membrane for a short distance between said second membrane and deck.
 7. A method of constructing a single ply membrane roofing system applied to a roof deck; said system comprising a first membrane with a longitudinally extending front free edge to be secured to said roof deck by transversely spaced fasteners, said membrane system having a second membrane with an edge portion rearwardly overlapping said first membrane edge and hot air or dielectric bonded to said first membrane via a continuous weld bond along the rear edge of said second membrane such that said first membrane edge projects forwardly from said weld bond to define a fastening projection extending forwardly from said free edge, comprising: a. with said system applied to said roof deck, maintaining said second membrane peeled upwardly back from said bond and fastening projection and placing transversely spaced apart fasteners into said deck to secure said fastening projection of said first membrane to said deck; b. with said second membrane in peeled back position applying a fast drying liquid adhesive over said fastening edge and fasteners from said bond forwardly and onto only a portion of said roof deck forwardly of said first membrane to provide a continuous adhesive coating on said first membrane projection, said fasteners, and a portion of said deck forwardly adjacent to said fastening projection, while also applying an adhesive coating to the underside of said membrane to an extent to cover the adhesive coating applied to said fastening projection and deck; and c. lowering said second membrane to cover and adhere to said coating on said fastening projection, fasteners, and deck portion. 